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Climbing through the Southern Alps, State Highway 94 is one of the highest and most scenic highways in New Zealand. It includes the Milford Road which stretches from Te Anau through Fiordland National Park to one of New Zealand’s major tourist attractions – Milford Sound.

The impacts of weather on the Milford Road can be severe. The high-altitude alpine conditions, a steep and rugged terrain that can be beset by floods and avalanches can pose significant risks. Indeed the road closed during winter until the late 1970s when tourist and fishing interests successfully lobbied for year-round operations.

The Milford Road Alliance

The Milford Road Alliance is a partnership between the NZ Transport Agency and Downer NZ to ensure the safe and efficient management of activities on State Highway 94 between Te Anau and Milford Sound.

It encompasses the safety of those working on the road, and the 700,000 people per year who use the road to visit the Sound. The partnership is responsible for the maintenance of the highway and the Homer tunnel, incident response, and an avalanche control programme which is critical in the winter season (May to November) when snow, ice and risk of avalanches can make safe driving difficult and cause road closures.

The Alliance team is based in Te Anau. This helps ensure that local knowledge and experience is applied to decisions about the operation of the highway and timely response to issues that can quickly arise in a fast-changing alpine environment.

New MetService weather services

To keep the road safely open as much as possible, the Alliance operates specialised weather and environmental data acquisition devices at both road and mountain levels. Information from these systems is supplied to MetService forecasters to provide regular expert interpretation.

For the 2017 winter season, MetService is providing the Alliance in Te Anau with several new and enhanced forecast services, including severe weather threat matrices covering the threat of snow, strong winds, and heavy rain with Free Air Freezing Level (FAFL). In addition, animating rainfall, snow and cloud ceiling forecast maps are being provided. Site-specific rainfall and temperature probability forecasts compete the picture in term of value-added forecast services. On top of this, significant improvements to the distribution and communication of data and forecasts have been made.

The new services complement those currently provided by MetService to the Alliance and are designed to assist informed decision-making about the management of the road at an operational level, including mitigating the risks posed by avalanches.

Quote from Kevin Thompson

“Without the experts at the MetService we would struggle to get that multiday look into the weather future that is critical for keeping the Milford Road open as much as we can. Our relationship with MetService goes back a long way – these additional weather services move us into a new space of automated, highly-visual but detailed information,” Kevin Thompson, Milford Road Alliance Manager.

Avalanche hazard alerting for the Milford Road

The avalanche hazard forecast is compiled from information that includes existing avalanche start zone snow-pack conditions (snow pit studies), current weather observations from automated road and mountain weather stations that transmit data to MetService forecasters, the weather forecast and local knowledge of avalanche activity. When a low avalanche hazard is posted on the information signs on the Milford Road, the road is open. If a moderate avalanche hazard is posted there is a risk of avalanches reaching the road and the road could be closed at any time. When a high avalanche hazard is posted, the road is closed.